The recent market trend of the audio industry requires high quality reproduction in response to the prevalence of digital audio devices represented by DVD.
Meanwhile, in terms of the environment around houses and vehicles, there is a strong demand to save space and energy.
As a speaker device that can satisfy the above demand, a speaker device which is small and excellent in deep-bass reproduction is required to be developed.
However, if a speaker cabinet of the speaker device is made small, it is difficult to reproduce bass due to the influence of the acoustic stiffness that the speaker cabinet exhibits.
FIG. 8 is a view illustrating a conventional speaker device. The conventional speaker device includes cabinet 101, speaker unit 102 provided in cabinet 101, and pressure adjustor 103 disposed inside cabinet 101.
In the conventional technique, in order to reliably reproduce bass even with a small speaker device and to solve a problem of limitation in bass reproduction which is determined by the cabinet volume, pressure adjustor 103 represented by activated carbon or the like is disposed inside cabinet 101.
Next, the operation of the speaker device will be described. When an electric signal is applied to speaker unit 102, the internal pressure of cabinet 101 changes, so the internal pressure of the cabinet in which pressure adjustor 103 is disposed changes. Air molecules are adsorbed onto pressure adjustor 103 or emitted due to the pressure change, whereby the internal pressure change of cabinet 101 is suppressed.
In this manner, for the conventional speaker device, cabinet 101 operates as a cabinet consistently retaining a large volume. Accordingly, even if the cabinet is compact, it is possible to perform bass reproduction as if speaker unit 102 is mounted on a large cabinet.
That is, pressure adjustor 103 such as activated carbon disposed inside cabinet 101 of the conventional speaker device exhibits an excellent bass reproduction function depending on the contact area thereof with air.
However, in order to satisfy a required minimum level of bass reproduction function, pressure adjustor 103 needs to have a contact area with air to meet the requirement. That is, in order to secure a sufficient contact area with air, a certain amount of pressure adjustor 103 needs to be disposed inside cabinet 101.
Meanwhile, recently, the thinning of flat screen TVs has accelerated, and as a result, the space in which pressure adjustor 103 can be disposed is getting smaller.
As a countermeasure for this, for example, a method is considered in which the activated carbon used as pressure adjustor 103 is made into fine powder to enlarge a specific surface area of the activated carbon.
This method aims to reduce the volume of the activated carbon in cabinet 101 by reducing the necessary weight of the activated carbon while securing the bass reproduction function by increasing the contact area per unit weight of the activated carbon with air.
Generally, the conventional speaker device employs a configuration in which the activated carbon is put in a bag formed of unwoven fabric or the like to fix the position of the activated carbon. Consequently, the above solution has a problem in that the powdered activated carbon leaks from gaps of the bag to the inside of cabinet 101.
The invention solves the problem and provides a pressure adjustor which acts effectively even in space saving. The invention also provides a speaker device which exhibits an improved bass reproduction function using the pressure adjustor.
As information regarding documents of prior art relating to the invention of the present application, for example, Patent Literature 1 is known.